Duty cycle improvement for human power generation

ABSTRACT

An electric power generation system is disclosed. The electric power generation system includes a string configured to be pulled; a bobbin configured to rotate when the string is unwound from the bobbin as it is being pulled; an electric power generator having a rotor wherein the rotor is mechanically coupled to the bobbin; and a mass attached to the rotor to store rotational energy and to output rotational energy while the string is being wound around the bobbin as the string is retracted.

CROSS REFERENCE TO OTHER APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. ______ (Attorney Docket number 25564-12168) entitled SMART HUMANPOWER GENERATION filed 29 Nov. 2006 which is incorporated herein byreference for all purposes.

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/864,772 entitled SMART HUMAN POWER GENERATION filed 7 Nov. 2006which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Modern appliances provide many useful functions. Typically, appliancesrequired power to function. In some cases, the power is provided byelectricity that is distributed by infrastructure enabling convenientaccess (e.g., from a wall outlet). In other cases, batteries are used.However, in some situations infrastructure is not present (e.g., inremote areas or in third world countries) and/or batteries are notavailable or cannot provide sufficient power.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a diagram illustrating an embodiment of a human powergenerating system.

FIG. 2 is a block diagram illustrating an embodiment of a human powergenerating system.

FIGS. 3A and 3B are diagrams illustrating embodiments of a human powergenerating system.

FIGS. 4A and 4B are diagrams illustrating embodiments of a case for ahuman power generating system.

FIGS. 5A and 5B are diagrams illustrating embodiments of a shaft, sealedbearing, and bobbin of a human power generating system.

FIG. 6 is a diagram illustrating an embodiment of bobbin and springrewinder of a human power generating system.

FIGS. 7A, 7B, and 7C are diagrams illustrating embodiments of pullingconfigurations for a human power generating system.

FIGS. 8A and 8B are block diagrams illustrating embodiments of a shaft,sealed bearing, and bobbin of a human power generating system.

FIGS. 9A and 9B are diagrams illustrating embodiments of fairlead holes.

FIGS. 10A and 10B are block diagrams illustrating embodiments of agenerator.

FIG. 11 is a diagram illustrating an embodiment of the wiring of astator and the magnets and inertial mass of a rotor.

FIGS. 12A, 12B, and 12C are diagrams illustrating embodiments of a humanpower generating system.

FIG. 13 is a diagram illustrating an embodiment of an integral anchoringattachment for a power generating unit.

FIGS. 14A and 14B are diagrams illustrating embodiments of connectorsystems for a power generating unit case.

FIGS. 15A and 15B are graphs illustrating the power generated from ahuman power generating system in two embodiments.

FIG. 16 is a diagram illustrating an embodiment of a circuit board.

FIG. 17 is a diagram illustrating an embodiment of an output cable andconnector.

FIG. 18 is a diagram illustrating an embodiment of a retraction circuit.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess, an apparatus, a system, a composition of matter, a computerreadable medium such as a computer readable storage medium or a computernetwork wherein program instructions are sent over optical orcommunication links. In this specification, these implementations, orany other form that the invention may take, may be referred to astechniques. A component such as a processor or a memory described asbeing configured to perform a task includes both a general componentthat is temporarily configured to perform the task at a given time or aspecific component that is manufactured to perform the task. In general,the order of the steps of disclosed processes may be altered within thescope of the invention. As used herein, the term ‘processor’ refers toone or more devices, circuits, and/or processing cores configured toprocess data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Human power generation is disclosed. A durable handheld portable humanpower generation system that is able to provide sufficient power tosupply an appliance such as a computer has a number of constraintsplaced on its system. For example, durability implies keeping the numberof breakable (e.g., moving) parts down, and handheld and portable implyconstraining the size of the unit. Gears can be used to increase thespinning speed of a generator to increase the output voltage, but havethe draw back of taking up space and being a moving part that can wearout.

A gearless power generating unit is disclosed. A string is configured tobe pulled. The string is configured such that a large motion (e.g., afull arm pull, a step, etc.) is used to pull the string. A bobbin isconfigured to rotate when the string is unwound from the bobbin as thestring is pulled. An electric power generator having a rotor that isconfigured to rotate such that the number of rotations of the rotor andthe bobbin is 1:1 when the string is being pulled. The string is rewoundon the bobbin when the string is retracting. In various embodiments, aspring, a motor driven using a retraction circuit (e.g., the electricpower generator used as a motor), or any other appropriate force sourceis used to retract the string. The bobbin is coupled to a shaft. Theshaft is coupled to a clutch, and the clutch is coupled to the rotor ofthe electric power generator. The clutch enables the shaft rotation whenthe string is being pulled to rotate the rotor. The clutch does notenable the shaft rotation when the string is being retracted to rotatethe rotor.

In some embodiments, when the string is being retracted, the powergenerating unit can continue to output power if the power is stored in arotating mass (e.g., a steel cap included as part of the rotor), abattery or a capacitor. In some embodiments, an output power limiter isused to limit output power of the power generating unit such that outputpower is available when the string is being retracted by ensuring thatthere is power remaining in the stored rotating mass, battery, orcapacitor that can be drawn on during the time when the string isretracting.

In some embodiments, retraction of the string is caused using a secondstring. The second string is wound on the bobbin such that when thefirst string unwinds, the second string winds, and when the secondstring unwinds, the first string winds. A user can pull alternately onone string and then the other. A spring or motor is not required torewind the string, and a clutch is not required to connect the shaft tothe rotor. A mass or electrical storage is also not required to enablethe power generating unit to output power when the first string isretracted. In some embodiments, the first and second string comprise onestring, wherein the middle of the string is coupled to the bobbin andone end of the string is used as the first string and the other end ofthe string is used as the second string.

In some embodiments, the string is anchored at one end to the case ofthe power generating unit. The other end of the string is wound andunwound on the bobbin. The string is pulled by pulling on a wheel aroundwhich the string is passed. Pulling on the wheel unwinds the string fromthe bobbin on one end and pulls against the other end anchored on thecase. A pull of the wheel of a distance ‘x’ away from the case causesthe string to be unwound a distance twice ‘x’ from the bobbin. A usercan generate more power using the extra wheel configuration since thebobbin will rotate twice as fast. The extra wheel configuration acts asa pulley. A user pulls on a handle which is coupled to the wheel.

In some embodiments, a power generating unit is anchored to a fixedobject enabling a user to operate the power generating unit withoutholding the unit in one hand. The power generating unit is anchoredusing an integral anchoring attachment. For example, a strap is coupledto the power generating unit case on both ends, where one end is coupledusing a detachable coupler (e.g., a hook, a clip, a snap, etc.).

The electric power generating unit includes a sealed chamber and achamber that can be opened. The sealed chamber protects the electricpower generator from environmental contamination. The chamber that canbe opened allows the string, bobbin, and spring (if appropriate) to beaccessed. The sealed chamber is sealed using a sealed bearing around ashaft between the sealed chamber and the chamber that can be opened. Thesealed chamber is sealed using the bottom of the case coupled to themiddle hour-glass shaped case.

In various embodiments, a power generating unit is mechanically coupledto an animal, the wind, a water wheel, or any other appropriate sourceof mechanical energy.

FIG. 1 is a diagram illustrating an embodiment of a human powergenerating system. In the example shown, user 100 holds power generationunit 102 in hand 104. User 100 pulls on string 106 using hand 108. Insome embodiments, hand 108 pulls on a handle (not shown in FIG. 1) thatattaches to string 106. String 106 mechanically causes a generator inpower generation unit 102 to produce electric power. String 106 has alength that is sufficient to allow a long pulling motion from user 100.In various embodiments, one hand is used to pull on string 106, twohands are used to pull on string 106, one foot/leg is used to pull onstring 106, two feet/legs are used to pull on string 106, or any otherappropriate human mechanical motion.

In some embodiments, an appropriate mechanical motion source other thanhuman is used to pull on string 106—for example, an animal motion, awind motion, etc.

FIG. 2 is a block diagram illustrating an embodiment of a human powergenerating system. In the example shown, mechanical power source 202 iscoupled to electrical power generator 204. Electrical power generator204 generates power using the motion generated by mechanical powersource 202. Electrical power generator 204 provides a signal indicatingmechanical activity (e.g., revolutions per minute (RPM) due tomechanical power source 202 input to electrical power generator 204) tocontroller and memory 212. Controller and memory 212 process informationprovided by the signal indicating mechanical activity and providefeedback to mechanical power source 202 (e.g., to a user pulling on astring). Feedback to mechanical power source 202 is provided using userfeedback device 214. In various embodiments, user feedback device 214comprises a light, a variable intensity light, a flashing light, avariable frequency flashing light, a sound, a variable pitched sound, avariable intensity sound, a vibration generator, or any otherappropriate feedback device. In various embodiments, user feedbackprovides information regarding desired pacing of pulls, power generated(e.g., over/under power ratings), or any other appropriate user feedbackinformation.

Electrical power generator 204 provides alternating current generatedpower to rectifier 206. Rectifier 206 rectifies the alternating currentgenerated power output to provide direct current power output. Invarious embodiments, the voltage of the direct current power output isconverted to a higher or a lower voltage and/or smoothed using acapacitor, or any other appropriate output conditioning. Rectifier 206outputs to control gate 208. Control gate 208 is able to switch thepower input to control gate 208 using a pulse width modulated switchbefore outputting to battery 210. Control gate 208 is switched based ona control signal from controller and memory 212.

In various embodiments, the rectifier is a passive rectifier or is anactive rectifier (e.g., a synchronous rectifier). In some embodiments,the control gate 208 and rectifier 206 are combined using the switchesof the active rectifier to pulse width modulate the output.

In some embodiments, there is no feedback provided to mechanical powersource 202.

In various embodiments, mechanical power source 202 comprises a stringbeing pulled, two strings being pulled, a bicycle, a rowing machine, astep machine, a treadmill, a windmill, a water wheel, or any otherappropriate mechanical power source. In some embodiments, a rotatingmechanical power source is coupled to the rotating rotor of the powergenerating unit without the use of a string to cause a bobbin to rotate.

In various embodiments, control gate 208 outputs to a device such as alaptop, a lamp, an LED light source, a cell phone charger, a radio, anentertainment device, a flashlight, a water purifier (e.g., a UV waterpurifier), or any other appropriate device requiring electrical power.In various embodiments, control gate 208 is coupled to battery 210 or acapacitor to condition the power output from control gate 208. Invarious embodiments, the power stored in battery 210 can be used to runany appropriate device requiring electrical power.

In some embodiments, the average electrical power output from the deviceis at least 10 W. There are many consumer devices that consume <1 W ofpower (e.g., cell phones, iPods™, Gameboys™, global positioning systemdevices, cameras, lighting, etc.). Because there have been severalpsychological studies that show that people need at least a 10:1 rewardto effort ratio for them to feel like an endeavor is worthwhile, a usageratio of at least 10 to 1 (i.e., 10 minutes of use for 1 minute ofeffort) is targeted. Therefore, 10 W is a useful target for the designof the human power generating system.

FIGS. 3A and 3B are diagrams illustrating embodiments of a human powergenerating system. In the example shown in FIG. 3A, power generatingunit 300 is shown in a top view with a line 301 indicating a cut viewline for FIG. 3B. In the example shown in FIG. 3B, power generating unitincludes bottom of case 302, middle hour glass of case 304, top of case306. String 308 is wrapped around the center of bobbin 310. String 308is secured to bobbin 310 at one end. The other end of string 308 passesout a fairlead hole 309. The other end of string 308 is attached to ahandle that enables a user to pull string 308, unwinding string 308 frombobbin 310. Bobbin 310 rotates while string 308 unwinds. Once unwound,string 308 is rewound around bobbin 310 by turning bobbin 310 usingspring 312. The outer end of spring 312 is coupled to a housing that isin turn coupled to top of case 306 (not shown in FIG. 3B). The inner endof spring 312 is couple to bobbin 310 (not shown in FIG. 3B). Onunwinding of string 308, bobbin 310 compresses energy into spring 312.The compressed energy in spring 312 is used to rewind string 308 aroundbobbin 310.

In some embodiments, spring 312 is not included in power generating unit300 (e.g., a motor is used to rewind string 308 on bobbin 310 or asecond string on bobbin 310 is used to rewind a first string such asstring 308).

On unwinding of string 308, bobbin 310 rotates and turns shaft 314.Shaft 314 is coupled to bobbin 310 by having a keyed hole in bobbin 310into which a corresponding keyed shaft 314 mates. In variousembodiments, the keyed hole comprises a “D” shaped hole, a star shapedhole, a square hole, a hexagonal hole, a single flat, a dual flat,splined, or any other appropriate keyed hole enabling a rotation ofbobbin 310 to be transmitted to shaft 314. Shaft 314 is coupled tosealing bearing 316. Sealing bearing 316 seals the lower chamber fromthe upper chamber. The upper chamber can be opened by opening top ofcase 306 and separating top of case 306 from middle hour glass of case304. Opening the upper chamber allows access to the keyed end of shaft314, bobbin 310, string 308, and spring 312. The lower chamber is sealedto prevent environmental contamination from affecting the electroniccomponents in the lower chamber.

The lower chamber contents include clutch 322, rotor 324, stator 326,and circuit board 328. Clutch 322 couples shaft 314 to rotor 324. Clutch322 enables a rotation of bobbin 310 to be transmitted to rotor 324 whenstring 308 is being unwound (e.g., as a user pulls string 308). Rotor324 rotates with a ratio of 1:1 with a rotation of bobbin 310. Clutch322 does not enable a rotation of bobbin 310 to be transmitted to rotor324 when string 308 is being rewound (e.g., as string 308 is rewound onbobbin using, for example, a spring force).

Rotor 324 includes magnets (not indicated in FIG. 3B). In someembodiments, rotor 324 includes an inertial mass (not indicated in FIG.3B). Stator 326 includes wire windings in which the current is generatedfrom the motion of bobbin 310 and rotor 324.

Handle 330 detaches from the top of the hour glass case and is attachedto one end of string 308 after passing out fairlead hole 309. Handle 330can be pulled by a user to cause rotation of bobbin 310. Strap 332 canbe used to anchor the power generating unit to a fixed object. A usercan then pull on handle 330 without holding the case of the powergenerating unit. A user fatigues less quickly if only pulling on handle330 and not also providing an anchoring force for the case than ifpulling and anchoring.

FIGS. 4A and 4B are diagrams illustrating embodiments of a case for ahuman power generating system. In some embodiments, the case of FIGS. 4Aand/or 4B comprise bottom of case 302, middle hour glass of case 304,top of case 306 of FIG. 3B. In the example shown in the projection viewin FIG. 4A, the case for a human power generating system includes top ofcase 400, middle hour glass of case 402, and bottom of case 404. Top ofcase 400 and middle hour glass of case 402 form upper chamber 406. Abobbin, on which a string is wound, is accessible upon opening of top ofcase 400. The string passes out of upper chamber 406 through fairleadhole 410. Middle hour glass of case 402 and bottom of case 404 formlower chamber 408. Lower chamber 408 is designed to prevent theenvironment from affecting the electronic components of the powergenerating unit. Bottom of case 404 seals against middle hour glass ofcase 402 so that lower chamber 408 is sealed from environmentalcontamination (e.g., dust, dirt, water, etc.). In various embodiments,the seal between bottom of case 404 and middle hour glass of case 402 issealed using ultrasonic welding, adhesive, an o-ring, a gasket, sealant,or any other appropriate way of achieving a seal.

In the example shown in the cut away view in FIG. 4B, the case for ahuman power generating system includes top of case 450, middle hourglass of case 452, and bottom of case 454. Top of case 450 and middlehour glass of case 452 form upper chamber 456. A bobbin, on which astring is wound, is accessible upon opening of top of case 450. Thestring passes out of upper chamber 456 through fairlead hole 460. Middlehour glass of case 452 and bottom of case 454 form lower chamber 458.Lower chamber 458 is designed to prevent the environment from affectingthe electronic components of the power generating unit. Bottom of case454 seals against middle hour glass of case 452 so that lower chamber458 is sealed from environmental contamination (e.g., dust, dirt, water,etc.). In various embodiments, the seal between bottom of case 454 andmiddle hour glass of case 452 is sealed using ultrasonic welding,adhesive, an o-ring, a gasket, sealant, or any other appropriate way ofachieving a seal.

FIGS. 5A and 5B are diagrams illustrating embodiments of a shaft, sealedbearing, and bobbin of a human power generating system. In the exampleshown in the exploded projection view in FIG. 5A, bobbin 500 includestop post 502 which is slit to hold one end of a spring. The springprovides a rewinding force on bobbin 500 enabling bobbin 500 to rewindthe string after a user has pulled the string to unwind it. Keyed end504 of shaft 506 is fit through sealed bearing 508 into the bottom ofbobbin 500. Keying enables a rotation of bobbin 500 to be efficientlytranslated to a rotation of shaft 506, while also allowing easy removalof bobbin 500 from shaft 506. Sealed bearing 508 holds shaft 506 andseals the opening between an upper and lower chamber of a case for ahuman power generating unit. Shaft 506 couples to a rotor of a generatorin the lower chamber of the case.

In the example shown in the compressed projection view in FIG. 5B,bobbin 550 includes top post 552 which is slit to hold one end of aspring. The spring provides a rewinding force on bobbin 550 enablingbobbin 550 to rewind string 560 after a user has pulled string 560 tounwind it. In various embodiments, string 560 is coupled to bobbin 550by passing through a hole in the axis post or side wall of bobbin 550and tying a knot or tying a knot with the rest of string 560 (e.g.,wrapping string 560 around the post of bobbin 560 and tying a knot tostring 560 on the side where it entered the hole), or any otherappropriate manner of coupling string 560 to bobbin 550. Keyed end ofshaft 556 is fit through sealed bearing 558 into the bottom of bobbin550. Keying enables a rotation of bobbin 550 to be efficientlytranslated to a rotation of shaft 556, while also allowing easy removalof bobbin 550 from shaft 556. Sealed bearing 558 holds shaft 556 andseals the opening between an upper and lower chamber of a case for thehuman power generating unit. Shaft 556 couples to a rotor of a generatorin the lower chamber of the case.

In some embodiments the string 560 is chosen to be between 0.5 and 2meters in length allowing a user to use a large motion when pulling onthe string. During typical use a user maintains a consistent pace ofpulling the string between 0.5 and 1.5 meters during each pull at a rateof one pull and one retraction each 0.5 to 1.5 seconds. The diameter ofbobbin 580 and the diameter of string 560 are both chosen to achieve acertain minimum rotational speed of shaft 506. In some embodiments thediameter of bobbin 580 is chosen to be 9 mm, and the string diameter ischosen to be between 1 and 2 mm. For a typical user pulling a string 1meter at a rate of one pull and one retraction each second, shaft 506will rotate at a speed of 3000 RPM. In some embodiments, the diameter ofbobbin 580 is chosen to be between 6 and 12 mm, and the string diameteris chosen to be between 0.5 and 4 mm. The speed of rotation of shaft 506can be increased by decreasing the diameter of bobbin 580 or thediameter of the string, but there are tradeoffs: a smaller diameter ofbobbin 580 will be more fragile and will also cause the string to rotatearound a smaller radius of curvature, thus impacting the lifetime of thestring; a smaller diameter string will have lower breaking strength andwill abrade faster, thus decreasing lifetime. A choice of diameter ofbobbin 580 and string diameter are made to achieve a long lifetime whilestill achieving a useful minimum rotational speed.

FIG. 6 is a diagram illustrating an embodiment of bobbin and springrewinder of a human power generating system. In the example shown,spring 602 outer end is coupled with holding case 604 by having tab 603at the outer end of spring 602 inserted into a slit of holding case 604(not shown in FIG. 6). Holding case 604 is coupled to top of case 600along with clamp ring 608 using one or more screws—represented in FIG. 6by screws 606. Clamp ring 608 loosely couples bobbin 612 to top of case600, such that bobbin 612 can freely rotate. Top post of bobbin 611remains engaged with spring 602 even after the rewinder assembly isremoved from the rest of the device. Slit 614 on top post of bobbin 611couples with inner end of spring 602 such that when string 610 is woundon bobbin 612, spring 602 unwinds. And, when string 610 is unwound onbobbin 612, spring 602 winds. In some embodiments, spring 602 isselected such that spring 602 does not “bottom out” upon fully unwindingstring 610 from bobbin 612. The diameter of the middle of the bobbin 613is designed in order that when string 610 is pulled bobbin 612 turnsrapidly enough to achieve a desired power output level. In someembodiments, the diameter is chosen to be in the range of 6 to 10 mm.

In some embodiments, before loading bobbin 612 with wound string 610 andspring 602 in its casing comprising clamp ring 608, holding case 604,and top of case 600 into the middle hour glass case (not shown in FIG.6), slit 614 of bobbin 612 is used to engage spring 602 and preloadspring 602.

FIGS. 7A, 7B, and 7C are diagrams illustrating embodiments of pullingconfigurations for a human power generating system. In the example shownin FIG. 7A, power generating unit 700 includes bobbin 706 which turnswhen string 702 winds or unwinds on bobbin 706. String 702 unwinds whenhandle 704 is pulled away from power generating unit 700. String 702winds when handle 704 is let loose and a spring or motor enables string702 to be retracted.

In the example shown in FIG. 7B, power generating unit 730 includesbobbin 740. Bobbin 740 turns when string 732 winds or unwinds on bobbin740 or when string 736 winds or unwinds on bobbin 740. String 732unwinds when handle 734 is pulled away from power generating unit 730.String 736 unwinds when handle 738 is pulled away from power generatingunit 730. String 732 winds when handle 734 is let loose and handle 738is pulled. String 736 winds when handle 738 is let loose and handle 734is pulled. In various embodiments, string 732 is the same or isdifferent from string 736.

In the example shown in FIG. 7C, power generating unit 760 includesbobbin 770 which turns when string 762 winds or unwinds on bobbin 770.String 762 unwinds when handle 768 is pulled away from power generatingunit 760. Handle 768 pulls on wheel 764 around which string 762 iswrapped. String 762 is anchored on power generating unit 760 usinganchor 766. For a pull of handle 768 a distance ‘x’ away from powergenerating unit 760, a length of string 762 two times distance ‘x’ ispulled off of bobbin 770. String 762 winds when handle 768 is let looseand a spring or motor enables string 762 to be retracted.

In some embodiments, more complex pulley arrangements are used insteadof the simple pulley shown in FIG. 7C. These pulley arrangements can beused when the mechanical pulling force is sufficient for pulling theincreased force required by using a complex pulley.

FIGS. 8A and 8B are block diagrams illustrating embodiments of a shaft,sealed bearing, and bobbin of a human power generating system. In theexample shown in the exploded projection view in FIG. 8A, bobbin 800includes keyed hole 802 which enables keyed end 810 of shaft 812 tocouple with bobbin 800. Bobbin 800 includes top winding space 804 for afirst string to be wound in a first direction and bottom winding space806 for a second string to be wound in a second direction. Pulling onthe first string unwinds the first string and rewinds the second string.Pulling on the second string unwinds the second string and rewinds thefirst string. Keyed end 810 of shaft 812 is fit through sealed bearing808 through bobbin 800. Bobbin 800 is secured on shaft 812 using clipring 814 which is inserted into clip ring slot 816 on shaft 812. Keyingenables a rotation of bobbin 800 to be efficiently translated to arotation of shaft 812. Sealed bearing 808 holds shaft 812 and seals theopening between an upper and lower chamber of a case for a human powergenerating unit. Shaft 812 couples to a rotor of a generator in thelower chamber of the case.

In the example shown in the compressed projection view in FIG. 5B,bobbin 850. String 854 is wound around bottom winding space (notindicated in FIG. 5B) of bobbin 850, and string 856 is wound around topwinding space (not indicated in FIG. 5B) of bobbin 850. Pulling on thestring 854 unwinds the string 854 and rewinds the string 856. Pulling onthe string 856 unwinds the string 856 and rewinds the string 854. Notethat no spring or motor is required to rewind string 856, so thathardware associated with string 856 is not used. In various embodiments,string 854 and/or string 856 is coupled to bobbin 850 by passing througha hole in the axis post or side wall of bobbin 850 and tying a knot ortying a knot with the rest of string 854 or string 856 respectively(e.g., wrapping string 854 around the post of bobbin 850 and tying aknot to string 854 on the side where it entered the hole), or any otherappropriate manner of coupling string 854 and/or string 856 to bobbin850. Keyed end 860 of shaft 862 is fit through sealed bearing 858 andthrough bobbin 850. Bobbin 850 is secured to shaft 862 using clip ring864. Keying enables a rotation of bobbin 850 to be efficientlytranslated to a rotation of shaft 862. Sealed bearing 858 holds shaft862 and seals the opening between an upper and lower chamber of a casefor the human power generating unit. Shaft 862 couples to a rotor of agenerator in the lower chamber of the case.

When using bobbin 850 (or bobbin 800), a restoring spring is not used.Further, an inertial mass for storing energy during the retraction of astring is also not used. A clutch is not required to only transmitrotation of bobbin 850 (or bobbin 800) to a generator rotor in onerotational direction.

FIGS. 9A and 9B are diagrams illustrating embodiments of fairlead holes.In the example shown in FIG. 9A, middle hour glass case 900 includes anopening for fairlead 902. Fairlead 902 creates a fairlead hole throughwhich a string can pass. The fairlead hole is designed to minimize wearon the string as the string is pulled out and retracted in through thefairlead hole. Fairlead 902 is designed such that the string spends aslittle time against the side wall of fairlead 902 as possible (e.g., theopening is bigger than the diameter of the string—for example, anopening of approximately 3.75 mm by 27 mm with a string diameter of 1 to2 mm). Also, the edge of fairlead 902 is given a profile that reducesthe angle of bending when the string bends around fairlead 902. Invarious embodiments, an elliptical curve, a substantially elliptical, aportion of an elliptical curve, or any other appropriate curve forreducing bending is used for the wall of fairlead 902.

In the example shown in FIG. 9B, middle hour glass case 930 includes anopening for fairlead 932. Fairlead 932 creates two fairlead holesthrough which two strings can pass. The fairlead holes are designed tominimize wear on the strings as each string is pulled out and retractedin through each fairlead hole. Fairlead 932 is designed such that thestring spends as little time against the side wall of fairlead 932 aspossible (e.g., the opening is bigger than the diameter of thestring—for example, an opening of between approximately 3.75 mm and 6 mmtall by 20 mm wide with a string diameter of 1 to 2 mm). Also, the edgeof fairlead 932 is given a profile that reduces the angle of bendingwhen the string bends around fairlead 932 for a typical use. In variousembodiments, an elliptical curve, a substantially elliptical, a portionof an elliptical curve, or any other appropriate curve for reducingbending is used for the wall of fairlead 932.

FIG. 9C is a block diagram illustrating an embodiment of a fairleadwall. In the example shown, string 960 bends around fairlead wall 962. Atypical use has string 960 bent at small angles around fairlead wall962. For this case, a stretched shape similar to an ellipse has lessbending to string 960 than a common circular fairlead wall profile. Morebending leads to greater wear, so the stretched shape similar to anelliptical profile leads to longer string life.

FIGS. 10A and 10B are block diagrams illustrating embodiments of agenerator. In the example shown in the cut away view in FIG. 10A, shaft1014 is coupled to sealed bearing 1012. Shaft 1014 has keyed end 1016which couples to a mechanical energy source (e.g., a bobbin caused torotate by pulling a string). Shaft 1016 is coupled to clutch 1006.Clutch 1006 allows rotation of shaft 1016 to be translated to a rotationof rotor in one direction (e.g., the direction of rotation when a stringis pulled rotating a bobbin coupled to shaft 1016). In some embodiments,clutch 1006 comprises a needle roller clutch. Clutch 1006 is coupled torotor cap 1002 using hex nut 1000. Rotor cap 1002 is coupled to magnetring 1004. Bearing 1008 allows clutch 1006 to turn and stator 1010 toremain stationary. In some embodiments, inertial mass stores energy whena string is retracting, and so rotor cap 1002 is made more massive(e.g., made out of steel, made of two metals such as lead and steel). Insome embodiments, inertial mass does not store energy when a string isretracting, and so is kept as light as possible (e.g., made out ofplastic)—for example, in the push-pull string configuration shown inFIG. 7B.

In the example shown in the perspective view in FIG. 10B, shaft 1044 iscoupled to sealed bearing 1042. Shaft 1044 has keyed end 1046 whichcouples to a mechanical energy source (e.g., a bobbin caused to rotateby pulling a string). Shaft 1046 is coupled to clutch 1036. Clutch 1036allows rotation of shaft 1046 to be translated to a rotation of rotor inone direction (e.g., the direction of rotation when a string is pulledrotating a bobbin coupled to shaft 1046). In some embodiments, clutch1036 comprises a needle roller clutch. Clutch 1036 is coupled to rotorcap 1032 using keyed torque transmitter 1030 (e.g., a hex nut). Invarious embodiments, keyed torque transmitter 1030 comprises a star nut,a square nut, a double-D nut, a D nut, a hex nut, or any otherappropriate shape enabling firm or non-slipping coupling between aclutch and a rotor. If rotor cap 1032 is made of a soft material such asplastic, and the keyed torque transmitter 1030 is not included, then theclutch 1036 will slip when delivering torque to rotor cap 1032. Rotorcap 1032 is coupled to magnet ring 1034. Bearing 1038 allows clutch 1036to turn and stator 1040 to remain stationary.

FIG. 11 is a diagram illustrating an embodiment of the wiring of astator and the magnets and inertial mass of a rotor. In the exampleshown, inertial mass 1100 is coupled to magnets that alternate theirpolarity. In some embodiments, the inertial mass comprises a steel capwith an outer diameter of approximately 70 mm. For example, magnet 1102and magnet 1104 present a magnetic field with opposite polarities to astator core and stator windings such as stator core 1106 and windings1108. In some embodiments, inertial mass 1100 comprises a steel ringwith inner radius approximately 65 mm, outer radius approximately 70 mm,height approximately 20 mm, and mass 200 g. In some embodiments,windings 1108 are configured in 3 phases, such that every third armatureis connected together. In some embodiments, windings 1108 comprise 30turns of wire per armature, and the wire is 0.6 mm in diameter such thata rotational speed on the motor of 3000 RPM results in an open-circuitvoltage of 18.3 V, and when connected to a 10 Ohm load the voltage is11.3 V. Windings 1108 are designed such that the trade off of the sizingof the wire, due to spatial constraints, and the length of the wire, dueto a resistance constraint/power loss constraint, are appropriately madeto achieve a human power generating unit capable of delivering 20 W intoa target device load when the generator is rotating at 3000 RPM.

In some embodiments, inertial mass 1100 is designed such that when auser operates the power generating unit pulling the string to achieve arotation of the rotor of 360° rotations per minute (RPM), the powergenerating unit is able to provide constant power of 15 W by storingenergy in the rotating inertial mass when the string is unwinding andthen delivering that stored energy during the rewinding of the string.The energy output from the device is limited to 15 W during the stringunwinding so that the extra energy can be stored as rotational energy inthe inertial mass.

An electrical power generator may be modeled by a speed-controlledvoltage source, in series with a Thevenin resistance. The voltage of thesource is linearly proportional to the shaft speed of the electricalpower generator. Therefore, the maximum power that may be drawn from theelectrical power generator is proportional to the square of the shaftspeed:

V _(—) oc=k*omega

P_max=1/2V _(—) oc*1/2I _(—) sc

I _(—) sc=V _(—) oc/R_thevenin

Therefore, P_max=V_oc

2/(4*R_thevenin)=k

2*omega

2/(4*R_thevenin). It may be shown that the maximum power point for anyparticular shaft speed is at half the open-circuit voltage, and half theshort-circuit current.

If a small radius generator is used, the magnet mass that can beeffectively used is small. This means the amount of energy absorbed perrotation is also small. A problem is that this dictates low poweroutputs for reasonable shaft rotation speeds. In other words, a smallradius results in a small value of k, above. To couple the electricalpower generator effectively to human body motions without the use ofgears, a electrical power generator must be chosen with large enough k.Since k varies as the physical volume of the electrical power generator,this condition dictates, for a given magnet quality, a minimum physicalvolume for the electrical power generator.

In designing an electrical power generator with a sufficiently largeenough physical volume, one may choose to make it axially long and/orradially fat. But while volume is proportional to r

2*length, the area of magnets required is proportional to only r*length.In order to make economic use of magnets, it is advantageous to maximizer. In some embodiments, short, fat generators, are thus chosen typicallywith a diameter to length ratio of between 4 and 6, although otherratios can also be used.

Once the armature shape of the electrical power generator is chosen, awire diameter is selected for the windings to match the output voltageat a humanly realizable speed, to the voltage of the batteries beingcharged, or the desired input voltage of the equipment to be run. Thisspeed is called the “cut in” speed.

In order to be able to modulate the coupling electronically, the cut-inspeed should be lower than the average expected use speed, called“design speed” throughout this specification. In some embodiments, thecut-in speed is chosen to be about one third of the design speed.

FIGS. 12A, 12B, and 12C are diagrams illustrating embodiments of a humanpower generating system. In the example shown in FIG. 12A, user 1200using hand 1202 and hand 1204, pulls on string 1203 and string 1205,respectively, which are coupled to power generating unit 1206. String1203 and string 1205 cause a rotor to turn in power generating unit 1206and, thereby, electric power to be generated. To ease user 1200 pullingon string 1203 and string 1205 power generating unit 1206 includes anintegral strap 1208 that enables power generating unit 1206 to beanchored to a fixed object (e.g., fixed object 1210). In variousembodiments, strap 1206 is anchored to a strap, a tree, a post, a fixedring, a tether, or any other appropriate object to anchor powergenerating unit 1206.

In the example shown in FIG. 12B, user 1230 using foot 1232 and foot1234, pulls on string 1233 and string 1235, respectively, which arecoupled to power generating unit 1236. String 1233 and string 1235 causea rotor to turn in power generating unit 1236 and, thereby, electricpower to be generated. To enable user 1230 pulling on string 1233 andstring 1235 power generating unit 1236 includes an integral strap 1238that enables power generating unit 1236 to be anchored to a fixed object(e.g., belt 1240).

In the example shown in FIG. 12C, user 1260 using hand 1262 and hand1264, pulls on string 1263 and string 1265, respectively, which arecoupled to power generating unit 1266. String 1263 and string 1265 causea rotor to turn in power generating unit 1266 and, thereby, electricpower to be generated. To ease user 1260 pulling on string 1263 andstring 1265 power generating unit 1266 includes an integral strap 1268that enables power generating unit 1266 to be anchored to a fixed object(e.g., foot 1270).

FIG. 13 is a diagram illustrating an embodiment of an integral anchoringattachment for a power generating unit. In the example shown, powergenerating unit 1300 includes post 1302 and post 1306. Strap 1304 isconstrained by post 1302 so that strap is integral to power generatingunit 1300. Strap 1304 is coupled to hook 1308 using pass through holes1310. Hook 1308 can be released from and can be hooked around post 1306.When hook 1308 is hooked around post 1306, power generating unit 1300 isanchored (e.g., as is shown in FIG. 13 where power generating unit 1300is anchored to pole 1312). Anchoring power generating unit 1300 enablesa user to generate power by pulling on the strings of power generatingunit 1300 (not shown in FIG. 13) with less fatigue then when alsoanchoring power generating unit 1300 by holding with a hand.Additionally, anchoring improves the use of the push-pull configurationas shown in FIG. 12A.

FIGS. 14A and 14B are diagrams illustrating embodiments of connectorsystems for a power generating unit case. In the example shown in FIG.14A, middle hour glass case 1400 includes a first connector system(e.g., threads 1402) for connecting middle hour glass case 1400 to topof case 1404. The chamber formed by middle hour glass case 1400 and topof case 1404 is designed to hold a primary mechanical turning sourcesuch as a bobbin that rotates as a string is wound or unwound inresponse to a string being pulled or retracted. In various embodiments,the first connector system comprises a bayonet connector system (e.g.,push and twist to lock), a sleeve mount (e.g., a cylinder, square, orhexagon that top of case 1404 slide down and locks via friction, setscrew, thumb screw, latch, etc.), a spline mount, a clip connectorsystem, a snapping connector system, or any other appropriate connectorsystem for connecting top of case 1404 and middle hour glass case 1400.

In the example shown in FIG. 14B, a second connector system (e.g., screwholes 1450) is also included in middle hour glass case 1452 (shown as atop view in FIG. 14B). The second connector system enables middle hourglass case 1452 to be attached or coupled to a secondary mechanicalturning source for turning the shaft of the power generating system ofmiddle hour glass case 1452. For example, a bicycle, turn wheel,propeller, a belt, or any other mechanical turning source for the shaftis coupled to the power generating system and the second connectorsystem is used to mount the power generating system appropriately. Thisenables the power generating system to take advantage of any mechanicalturning source of energy including animals, wind mills, exercise devices(e.g., bicycles, walkers, rowing machines, step machines, etc.), waterwheels, etc.

FIGS. 15A and 15B are graphs illustrating the power generated from ahuman power generating system in two embodiments. In the example shownin FIG. 15A, as indicated by region 1500 in the graph, power isgenerated during the time when the string is being pulled causing arotor in a generator to turn. In the example shown, output power islimited to 15 W. Power is not generated during the time when the stringis being retracted as indicated by region 1502 in the graph. X-axis ofthe graph indicates the amount of power generated, and y-axis of thegraph indicates time.

In the example shown in FIG. 15B, the output of the power generatingunit is essentially constant. In the time corresponding to when thestring is being pulled, energy that is generated is both output from theunit and also stored in a stored energy source. In the timecorresponding to when the string is being retracted, energy is drainedfrom the stored energy source. Time region when the power is constant1510 is larger than the time when the stored energy source cannot keepthe output power constant 1512. The stored energy source for FIG. 15Bcomprises a 0.3 F super capacitor. In the example shown, output power islimited to 15 W. X-axis of the graph indicates the amount of powergenerated, and y-axis of the graph indicates time.

In the example shown in FIG. 15C, the output of the power generatingunit is essentially constant. In the time corresponding to when thestring is being pulled, energy that is generated is both output from theunit and also stored in a stored energy source. In the timecorresponding to when the string is being retracted, energy is drainedfrom a stored energy source. Time region when the power is constant 1520is larger than the time when the stored energy source cannot keep theoutput power constant 1522. The stored energy source for FIG. 15Ccomprises an inertial mass that stores rotational energy. In the exampleshown, output power is limited to 15 W. X-axis of the graph indicatesthe amount of power generated, and y-axis of the graph indicates time.

In some embodiments, the output power generating unit output can befurther regulated using an output power limiter. The output powerlimiter determines the total power generated in a cycle of pulling andretracting and sets the overall output level such that a constant outputcan be achieved. In other words, the reserve power in the stored energysource is sufficient to provide the output power during the retractingof the string. Output power can be limited by switching a switch todisconnect the output from the power generation circuitry in the powergenerating unit.

In some embodiments, power output is limited by a receiving device(e.g., an input to a laptop power supply).

FIG. 16 is a diagram illustrating an embodiment of a circuit board. Insome embodiments, the circuit board of FIG. 16 comprises circuit board328 of FIG. 3B. In the example shown in top view of circuit board FIG.16, circuit board receives current at contact 1600, contact 1602, andcontact 1604 produced by generator from coils in stator. Diodes 1606,diodes 1608, and diodes 1610 rectify received current. Memory andcontroller 1612 provides feedback to user and controls output power.Feedback to user is provided using light emitting diodes 1614. Outputpower is controlled using switch 1616. Controlling output power alsocontrols a resistance a user feels when pulling a string connected togenerator. Output is connected to output contacts 1618.

FIG. 17 is a diagram illustrating an embodiment of an output cable andconnector. In the example shown, power generating unit 1700 outputspower using cable 1702. Cable 1702 is coupled to connector 1704 whichenables an electrical connection between cable 1702 and a circuit boardof power generating unit 1700 (e.g., contacts 1618 of FIG. 16).Connector 1704 provides strain relief with case of power generating unit1700 in the event that cable 1702 is pulled. Connector 1704 alsoprovides sealing of the sealed chamber holding the electronics andgenerator of the power generator unit against contamination (e.g.,water, dust, sand, etc.).

FIG. 18 is a diagram illustrating an embodiment of a retraction circuit.In the example shown, the circuit is used to have the generator act as amotor such that the generator can be used to retract the string backonto the bobbin. Motor 1800 has three phases which are connected bythree wires 1802 to six field effect transistors (FET's) 1804. FET's1804 are selectively turned on or off by the control lines 1806 comingfrom controller 1808. The output of FET's 1804 is to battery/load 1810.Monitor 1812 monitors the amount of power being delivered tobattery/load 1810.

In some embodiments, controller 1808 will selectively turn on/off FET's1804 in such a way that they will synchronously rectify the AC output ofthe motor 1800 and deliver the rectified DC power to battery/load 1810.In some embodiments, monitor 1812 provides a signal to controller 1808when the power is no longer being delivered, such as when a user hasfinished pulling on a string. When the power is no longer deliveredcontroller 1808 can use FETs 1804 to drive motor 1800 in such a way asto rewind a string onto a bobbin, using a portion of the energy storedin battery/load 1810. In this manner motor 1800 is used as both anenergy generator and also as a string rewinder.

In some embodiments, controller 1808 selectively turns on or off acontrol gate (not shown in FIG. 18) or FET's 1804 in order to adjust theamount of power flowing into battery/load 1810. In some embodiments,Hall effect sensors of motor 1800 measure the rotational speed of motor1800 and are monitored by controller 1808. When a user is pulling andunwinding the string from the bobbin, motor 1800 will produce power thatis rectified (e.g., by a diode rectifier) that passes to battery/load1810. Once the user has finished pulling, the rotational speed of themotor will drop below a certain threshold for a certain time (i.e., themotor slows down for example to <500 RPM for a time period of at least100 ms). Once the speed drops below the threshold, controller 1808 canselectively turn on and off FET's 1804 using standard motor commutationin such a way that the energy stored in battery/load 1810 is used torotate motor 1800 thereby rewinding the string onto the bobbin.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

1. An electric power generation system including: a string configured tobe pulled; a bobbin configured to rotate when the string is unwound fromthe bobbin as it is being pulled; an electric power generator having arotor wherein the rotor is mechanically coupled to the bobbin; and amass attached to the rotor to store rotational energy and to outputrotational energy while the string is being wound around the bobbin asthe string is retracted.
 2. A system as in claim 1, further comprisingan output limiter that limits the energy extracted from the rotatingrotor such that the electric power generation system can output powerboth when the string is retracted and when the string is pulled.
 3. Asystem as in claim 1, wherein the mass comprises a steel cap.
 4. Asystem as in claim 3, wherein the mass comprises a plurality of magnets.5. An electric power generation system including: a string configured tobe pulled; a bobbin configured to rotate when the string is wound aroundthe bobbin as the string is pulled; an electric power generator having arotor wherein the rotor is mechanically coupled to the bobbin; and anelectric storage device to store electric energy and output the storedenergy while the string is retracted.
 6. A system as in claim 5, furthercomprising an output limiter that limits the energy extracted from theelectric storage device such that the electric power generating systemcan output power both when the string is retracted and when the stringis pulled.
 7. A system as in claim 5, wherein the electric storagedevice comprises a capacitor.
 8. A system as in claim 7, wherein thecapacitor comprises a super capacitor.
 9. A system as in claim 5,wherein the electric storage device comprises a battery.
 10. A system asin claim 9, wherein the battery comprises one of the following: alead-acid battery, a lithium ion battery, or a nickel-cadmium battery.